Lubrication system



April 6, 1937. R. w. ZERCHER LUBRICATION SYSTEM V 2 Sheets-Sheet 1Zmventor Filed June 29, 1935 R. w. ZERCHER 2,076,332

LUBRIGATION SYSTEM 'Filed June 29, 1935 2 Sheets-Sheet 2 5W @mmm W 2/ W7mm ala-Nita (Ittgrneg S a s L 11% w an w mn A 6 iv. w n m, Nb wm on a I2 5 5%. 3 Lu 0 F q. Q i fi L. 1 Q 1 L 1 LV w 6 Patented Apr. 5, 1937 umro STATES FATE-T err-ice LUBRIGATION svs'rEM Robert W. Zercher, York,Pa., assignor to York Ice Machinery Corporation, York, Pa., acorporation of Delaware Application June 29, 1935, Serial No. 29,133

10 Claims. (01. 230206) This invention relates to lubricating means forrefrigeration systems of the type in which a plurality of compressorsoperate in parallel relation and supply compressed gas to arefrigerating circuit. 1

In systems of this character it is usual to lubricate the compressors bythe splash system in which the crank cases of the compressors act assumps for the lubricating oil and are in communication with the lowpressureside of the circuit. Where a plurality of compressors areoperated in parallel, it is usual to cut them in or out, in accordancewith the load on the refrigerating circuit, the control being eithermanual or automatic. Consequently, conditions arise where certain of thecompressors are idle when others are operating.

Frequently the lubricating oil flows in suspension in the gaseous orliquid refrigerant, and this is particularly true when therefrigerant isone of the recently developed types, such as that mon suction anddischarge lines, at such times as the crank case pressures of twocompressors'become equal. It has also been found to be'equallyimportant, as hereinafter explained, to prevent oil flow from one crankcase to another at all times when the crank case pressures are unequal.

Equalization of the oil level between the crank cases of the variouscompressors an be obtained by providing equalizing conne tions betweenoints of proper oil level in the various crank c es. A constantly openconnection is, however, not satisfactory, because the crankcasepressures of different compressors may'vary. When, for example, one ormore of the machines is idle, crank case pressure tends to build up inthemachine or machines which are active and this results in the oil fromthe crank case of an operating machine being displaced and transferredto the crank case of an idle machine. Obviously, such a condition mustbe avoided since it may result in acompressor running dry.

Consequently, it isproposed, according to this invention, to provideequalizing connections between the crank cases of the compressors, andto include in each connection a check valve having a moderate openingtendency. This valve will operate to prevent oil from being forced fromthe crank case of one machine to that of another by pressuredifferential developed between the crank cases of such machines, butwill not prevent the equalizing gravity flow of oil when ad- .jacentmachines are inactive or when the pressures are equalized.

The invention will be more fully understood when the followingspecification is read in conjunction with the drawings in which:--

Figure l is a diagrammaticalyiew of one form of refrigeration systemembodying this invention;

Figure 2 is a detail sectional view of a double check valve which may beused in carrying out this invention;

Figure 3 is a view similar to Figure 1, but showing a modifiedarrangement of oil equalizing connections, also embodying thisinvention; and

Figure 4 is a sectional view of a check valve suitable for use in thesystem of Figure 3.

For purposes of illustration the invention has been shown in Figure 1,as embodied in a simple refrigeration system of the direct expansiontype, although it is to be understood that it is of gen-" -eralapplication and may be used in connection with a system of the floodedtype or in any system in which a plurality of compressors are connectedin parallel with the refrigerating circuit and are capable ofindependent or conjoint operation.

Referring to Figure 1 the reference characters CI, C2 and C3 designatethree compressors connected inparallel relation on their high sides to.a common pressure line 8 leading 'to a condenser 9. The system includesa line H running from the condenser 9 to a liquid receiver 12; a line l3and an expansion valve I4 connecting the out flow of receiver I2 to theinlet of evaporator l5, and a return or suction line l6 connecting theevaporator with the low sides of the compressors Cl, C2 and C3 inparallel.

The three compressors shown will normally, 45

although not necessarily, be arranged'to be cut in serially according tothe load on the refrigerating circuit, and to be cut out serially inreverse order. For example, under light load conditions the compressor.CI may operate alone.

On falling loads machine C3 will cut out first, then machine C2 andfinally machine Cl.

Each of the compressors Cl, C2 and C3 has a crank case H which acts as asump for lubricating oil. Connected between the crank cases ll of thecompressors Cl and C2, at or below the normal oil level'therein, is anequalizing connection or line l8 containing a two-way check valve 20. Asimilar equalizing connection l9 containing a two-way check valve 21| isplaced between the compressors C2 and C3. If only two machines areused,- a single equalizing connection will be chamber 22 partiallyclosed at each end by a sleeve 23 threaded into the body 20 and havingslots 24 for the reception of a wrench or screw driver. The inner end ofeach of the sleeves 23 has a countersunk seat for sealing cooperationwith a ball check 26 which, under conditions of equal pressure at bothends of the chamber 22, gravitates to substantially the mid point ofthis chamber, as shown in Figure 2. When a pressure differential existsbetween the ends of the chamber 22, the ball 26 is forced into contactwith the seat 25 of one or the other of the sleeves 23 thereby closingthe equalizing connection against flow of lubricant. In moving tosealing engagement with either seat the ball is raised slightly againstthe attraction ofgravity. Consequently, the ball check may operate ineither direction to prevent flow of lubricant between the crank cases ofmachines having unequal pressures. When, however, the crank pressures oftwo connected machines become substantially equal, the ball 26 will fallaway from both of the seats 25. The oil flow will then be insufflcientto lift the ball to sealing position, leaving substantially unrestrictedconnection between the two ends of the chamber 22 and permittingequalizing flow of oil from one crank case to the other. It isunnecessary to provide an equalizing connection between the crank casesof compressors Cl and C3, because of the order in which the compressorsare put into and out of action. Hence no such connection is shown.Obviously the use of this additional connection is within the scope ofthe invention.

The operation of the two-way check in the complete system shown may bestated briefly as follows:

When the compressor Cl alone is operating, its crank case pressure willpredominate over that of the two idle machines. Consequently, the ball26 will move against the left hand seat 25 of valve 20 and prevent flowof oil from the crank case of machine CI'to that of machine C2. Ifmachine C2 then starts up, pressure between the crank cases of machinesCI andC2 will be substantially equalized and the check 20 will open,while the check 2| between machines C2 and C3 will close. If machine C3is likewise operating, both checks 20 and 2| will open, and the pressurewill besubstantially equalized among the three crank cases. When machineC3 shuts. down, the check 2| between that machine and C2 will close toprevent oil from being discharged from the crank case of C2 to that ofC3, and a similar operation of check 20 will occur when machine C2 shutsdown. When all of the machines shut down both checks will open and theoil level will equalize among the three machines. While the inventionhas been described in connection with a system including a plurality ofcompressors connected in parallel and adapted for serial operation, thepreferred arrangement is such that the compressors may operate in anyorder, and consequently flow of oil from one compressor to another isprevented whenever a pressure differential exists between any twomachines. Figure 3 of the drawings illustrates a system of thischaracter having the same evaporator, receiver and condenserarrangements as those shown in Figure 1.

Referring to Figure 3, thereference characters 31, 38 and 39 designatethree compressors having pressure connections 5, 6 and 'I, respectivelyto the pressure side 8 of the refrigerating circuit. Similarly thesuction connections 21, 28 and 29 of these machines are made to thesuction side l6 of the refrigerating circuit. n In this arrangement, thecompressors 31, 38 and 39 may operate in any order, as for example, whenthe system is subject to manual control. Under such circumstances theoperator would employ a number of machines commensurate with therefrigerating load, and would cut machines in or out, in accordance withvariations in this load. A failure of one of the machines might resultin a complete change in the order of operation, consequently, it isdesirable to have the oil equalization independent of the order in whichthe compressors are put into or taken out of operation.

As shown in the drawings, the oil equalizingconnection comprises a mainline 3| between the crank cases ll of the machines 31 and 39, and abranch line 33 interposed between the line 3| and the crank case ll ofcompressor 38. The oil equalizing connection has interposed between it,and each of the crank cases ll of the three compressors, a check valve32 preferably constructed' and arranged as shown in Fig. 4. All of thesevalves are similar, hence a description of one of them will suiiice.This check valve is generally similar in form to that shown in Figure 2,except that in this case the arrangement is such that the ball need seatin one direction only. The valve comprises a valve body 32 threaded at4| into the wall of a crank case I! and threaded at its opposite endsinto a nipple 42 adapted to form a pressure tight seal with the line 3|.The body of the valve 32 is preferably formed on the outside for thereception of a wrench. It contains a chamber 34 similar to the chamber22 of double check valve 20 previously described.- The end of chamber32, adjacent the crank case I1, is closed by a threaded sleeve 35 havinwrench slots 24, and preferably formed at its end, adjacent the ballcheck 36, with a flat face, since this ball check need have a sealingconnection at one, end only of chamber 34. The outer end of chamber 34contains a'second threaded sleeve 23 having slots 24 and being otherwisesimilar to the sleeves 23 described in connection with the double checkvalve previously described.

Consequently, when pressure is substantially equalized between theinside of one of the crank casesl'l and the line 3|, the ball 36gravitates to the position shown in Fig. 4. Whenever a. pressurediiferential is formed, however, so that the pressure within the crank.case I! predominates over that in line 3 I, the ball 36 will be liftedslightly and into contact with'the seat 25 on sleeve 23, thus sealingthe crank case I'll against escape of oil therefrom. As soon as pressurebetween the crank case and the line 3! is equalized,

the ball 36 will gravitate again to the position shown in Fig. 4 so asto permit free equalizing flow of oil from one crank case to anotherthrough the line 3| or the-line 3! and branch line 33, as the case maybe. It will be obvious that because of this arrangement of a ball checkassociated with each of the compressors 31, 38 and 39, there can be noflow of oil from one crank case to another, when a pressure diiferentialexists between any two machines. Rise in pressure within any one of thethree crank cases will cause the associated check valve 32 to close,thus cutting off the flow of oil through the equalizing connection.

It will be understood that the system shown in Figure 3 produces resultssimilar to those of the apparatus of Figure 1, except that it isentirely independent of the order in which the compressors start orstop, and a one-way check. valve is sufilcient, since a check valve'isassociated with each of the compressors. Consequently, the em- '25bodiment of the invention shown in Figure 3 ofiers a flexibility ofoperation which is not possible with the system shown in Figure 1.

The invention described is of particular utility in systems where thereis a marked tendency for 30 the lubricating oil to flow in suspension inthe .40 ating in parallel. Consequently, no limitations other than thosedirectly expressed in the claims are implied.

What is claimed is: 1. In a lubrication system, a circuit for a vola- 45tile liquid medium; a plurality of compressors connected in parallel insaid circuit and arranged to operate, one or more at a time, inaccordance with the load on said circuit, eachoi said com pressorshaving an oil sump subject to the suc- 0 tion pressure of the circuit; alubricating conduit connecting the sumps of said compressors; and meansin said conduit for preventing flow of lubricant from one sump toanother when a material pressure differential exists between them, 55but permitting equalizing flow between said sumps when their pressuresare substantially equal.

2. In a lubrication system, a circuit for a volatile liquid medium; atleast two compressors having individual suction connections andindividual 60 discharge connections with said circuit, and each havingan oil reservoir subject to the suction pressure of the circuit; alubricant level equalizing conduit connecting the reservoir of eachcompressor to the reservoir of the adjacent com- 5 pressor; and'means ineach of said conduits for permitting lubricant equalizing fiow betweenadjacent inactive compressors but preventing flow between an active andan inactive compressor.

3. In a lubrication system, a circuit for a vola- 70 tile liquid medium;at least two compressors con nected in said circuit in parallel relationto one another and adapted for simultaneous or individual operation; alubricant sump in each of said compressors subject to the suctionpressure of 75 the circuit; a lubricant'conduit connecting the ting freeequalizing flow between the sumps of the 5 compressors when theirpressures are equal.

4. In a lubrication system, a circuit for a volatile liquid medium; aplurality of compressors having individual suction connections andindividual discharge connections with said circuit; a 10.

lubricant sump associated with each of said compressors and subject tothe suction pressure of the circuit; a lubricant level equalizingconduit between each sump and another; and a two-way check valve in saidconduit, said valve being ar- 15 ranged to prevent lubricant flow fromthe sump of an active to that of an idle compressor and permittingequalizing flow between the sumps of idle compressors.

5. The combination of a closed circuitfor a 20 volatile liquid medium;at least two compressors connected in parallel in saidcircuit andcapable of independent and conjoint operation, said compressors being ofthe type in which lubrication is effected from a charge or oil carriedin the crank case, and the crank case is subject to the suction pressurein the system; a normally open oil level equalizing connection betweenthe crank cases of such compressors; and means effective when acompressor is idle to close the equalizing connection between its crankcase and the crank case of an active compressor.

6. The combination of a closed circuit for a volatile liquid medium; atleast two compressors connected in parallel in said circuit and capable.of independent and conjoint operation, said compressors being of thetype in which lubrication is efiected from a charge of oil carried inthe crank case, and the crank case is subject to the suction pressure inthe system; a normally open oil level l0 equalizing connection betweenthe crank cases of such compressors; and means responsive to pressuredifferential between the crank cases of the compressors, for at timesclosing said equalizing connection to prevent flow of oil from one crankcase to another.

v 7. In a lubrication system, a circuit for a volatile'liquid medium; .aplurality of compressors connected in parallel relation to one anotherto supply high pressure gas to saidcircuit, and to receive low pressuregas from, said circuit; an oil collecting reservoir in the low side ofeach of said compressors; an oil level equalizing conduit connecting allof said reservoirs together; and a two- Way check valve interposed insaid conduit be- 5 tween the reservoir of each compressor and that of anadjacent compressor, said valves being gravity operated to permitequalizing flow of oil from one compressor to another when the reservoirpressures are equal, but responsive to a pressure differential betweenadjacent compressors to prevent flow 01' oil from one compressor toanother. 7

8. In a'lubrication system, a circuit for a volatile liquid medium; apluralityofcompressors having their crank cases formed to act aslubricant reservoirs subject to the suction pressure of the circuit andalso subject to variable pressure depending upon whether they are activeor idle;

means forconnecting saidcompressors to said circuit in parallel relationto one another; a lubricant level equalizing conduit connecting all ofsaid reservoirs together; and a check valve interposed in said conduitbetween each compressor and another, said valve being biased by gravityto open position when two adjacent compressors are idle, and closed bythe pressure difierential existing when one of two adjacent compressorsis idle and the other is active.

9. In a lubrication system, a circuit for a volatile liquid medium; aplurality of compressors connected in parallel with said circuit, andhaving oil reservoirs subject to the suction pressure of the circuit;means for permitting equalizing flow of lubricant from the oilreservoinof one compressor to that of another when the pressures inthese reservoirs are substantially equal; and means responsive topressure differential between said reservoirs for preventing flow oflubricant from one reservoir to another.

10. The combination of a circuit in which a volatile liquid medium isconverted between the liquid and vapor phases by changes of pressure andtemperature, such circuit including a plurality of compressors connectedin parallel therein, and capable of individual and conjointxoperation,said compressors having oil sumps subject to the suction pressure, fromwhich sumps the compressors are lubricated and the circuit being soarranged that lubricant if entrained with the volatile medium will bereturned to at least one of said sumps; oil level equalizing connectionsbetween the sumps of respective compressors; and check valve meansinterposed in said equalizing connections; said check valve means havingan opening bias sufficient to maintain them open against differences inhydrostatic pressure occasioned by differences of oil level, butinsuflicient to maintain them open against difierentials of suctionpressure between different compressors, one of which is operating andthe other of which is inactive.

' ROBERT W. ZERCHER.

